1. Field of the Invention
The present invention relates to a process for preparing (S)-(+)-N-methyl-3-(1-naphthyloxy)-3-(2-thienyl)propylamine and its pharmaceutically acceptable salts with high enantiomeric excess (ee) and high chemical purity by using chiral compounds as an intermediate.
2. Description of Related Art
(S)-(+)-N-methyl-3-(1-naphthyloxy)-3-(2-thienyl)propylamine (Duloxetine®) hydrochloride salt is used as an antidepressant for medical therapy. There are various processes for preparing Duloxetine®. For example, U.S. Pat. No. 7,538,232 discloses a process for preparation of Duloxetine® by reacting (S)-3-methylamino-1-(2-thienyl)propan-1-ol and 1-fluoronaphthalene with potassium hydroxide in a mixed solvent system (i.e., DMSO and toluene) in order to preserve chiral integrity. However, due to different types of organic solvents used in the process for the preparation of Duloxetine®, cost of subsequent treatment increases. In addition, the usage of mixed organic solvents is disadvantageous to environmental protection. Therefore, there is still a need to provide a process for preparing chiral Duloxetine®.